Cosmic Concept: Visiting Asteroids With Fleets of Nanoprobes

Only the largest asteroids have enough gravity to allow a probe to enter their orbit. So, to study the litany of smaller ones—the debris from the early solar system—let's send a swarm of tiny explorers.

Exploration of asteroids has been limited to bodies large enough to allow a probe to enter its orbit. Smaller ones don't have enough gravity to send the same kinds of missions. Justin Atchison has a plan for that.

Atchison, a senior aerospace engineer at Johns Hopkins University's Applied Physics Laboratory, wants to explore small asteroid bodies by sending a fleet of smaller nanoprobes at them to make gravitational measurements and determine mass and other characteristics of the rocky—and little-understood—debris from our solar system's formation.

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The proposal, known as the Swarm Flyby Gravimetry, was recently awarded a Phase I grant in the NASA Innovative Advanced Concepts (NIAC) program. The goal of the swarm is to create a cheap, fast way to study asteroids by using dozens of microprobes that would scatter around an object in space. A larger probe would gather all the measurements of their movements around the asteroid and combine them into a more complete picture. (Nanoprobes need to be small and cheap, since losing a few in the process of taking the measurements is par for the course.)

"By fusing all of these measurements, it's possible to infer the asteroid's mass."

"Each object then represents a single measurement as its own trajectory is slightly pulled by the small asteroid," Atchison says. "By fusing all of these measurements, it's possible to infer the asteroid's mass, and possibly even discover features within that gravity field."

These nanoprobes could make important measurements that no standard probe could perform. And Atchison imagines they could do so in a number of ways. The probes could simply reflect light, which would help infer gravity by their position and the way they scatter around the asteroid. Another version might use simple probes armed with LEDs, which would use a similar concept, but light up rather than use reflective light, and use different LED colors to track movements of particular swarm members. Or Atchison could use a batch of small satellites equipped with active sensors measuring Doppler information before they crash into the asteroid, which would give the scientists more active data collection prior to crash. The latter is the least likely for now, he says, as it would require the probes to work and connect correctly in deep space. If they failed, the mission might be lost.

Over the next year the team will work on proof of concept and cost measurements, all to sort out the details of what the mission will ultimately become.

"There are a lot of exciting interplanetary missions coming up in the next decade, some of which will undoubtedly be fly-by asteroids, so I'm optimistic that there are opportunities to host this," Atchison says.